Machines such as, for example, dozers, loaders, excavators, motor graders, and other types of heavy equipment use hydraulic actuators coupled to a work implement for manipulation of a load. Such machines generally do not include shock absorbers and, thus, may pitch, lope, or bounce upon encountering uneven or rough terrain. The substantial inertia of the work implement and associated load tends to exacerbate these movements, resulting in increased wear of the machine and discomfort for the operator. Methods and systems for reducing the magnitude of the movements attributable to the work implement have been developed and are commonly referred to as “ride control.” One challenge with these systems is developing an efficient protocol for activating and deactivating ride control. Ride control is beneficial when traveling with or transferring a load. It is undesirable, however, to have ride control engaged when a machine is digging in a pile with a bucket because it dampens the force exerted by the bucket and exposes system components to potentially damaging pressure spikes.
One method of determining when to activate and deactivate ride control is described in U.S. Pat. No. 7,621,124 (the '124 patent) issued to Mizoguchi et al. on Nov. 24, 2009. The '124 patent describes a method and device for suppressing travel vibration for a working vehicle using a ride control valve that communicates or cuts off a bottom chamber of a boom cylinder from an accumulator. The '124 patent describes a method of activating ride control or controlling the ride control valve based on a pressure sensor and a travel state detecting sensor. The travel state detecting sensor may constitute a variety of sensors including, for example, a speed sensor, a sensor which can detect a speed gear of a transmission and a rotational speed of an engine, a sensor which can detect the speed gear of the transmission and a stroke position of an accelerator pedal, and a GPS sensor.
Although the system and method of the '124 patent may provide a protocol for activating and deactivating ride control, it may be less than optimal. Specifically, the system and method of the '124 patent may prevent ride control activation in certain operating situations where ride control may be desired, for example, when carrying or transferring a load at lower speed in a low gear.
The disclosed hydraulic system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.